it.unimi.di.mg4j.index
Class MemoryMappedIndex

java.lang.Object
  it.unimi.di.mg4j.index.Index
      it.unimi.di.mg4j.index.BitStreamIndex
          it.unimi.di.mg4j.index.MemoryMappedIndex

All Implemented Interfaces:

Serializable

public class MemoryMappedIndex
extends BitStreamIndex

A local memory-mapped bitstream index.

Memory-mapped indices are created by mapping the index file into memory using a MappedByteBuffer. The main advantage over an InMemoryIndex is that only the most frequently used parts of the index will be loaded in core memory.

Since:

1.2

Author:

Sebastiano Vigna

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.di.mg4j.index.BitStreamIndex

BitStreamIndex.PropertyKeys

Nested classes/interfaces inherited from class it.unimi.di.mg4j.index.Index

Index.EmptyIndexIterator, Index.UriKeys

Field Summary

protected ByteBufferInputStream

index The byte buffer containing the index.

Fields inherited from class it.unimi.di.mg4j.index.BitStreamIndex

bufferSize, countCoding, DEFAULT_BUFFER_SIZE, DEFAULT_FIXED_QUANTUM, DEFAULT_HEIGHT, DEFAULT_QUANTUM, FIXED_POINT_BITS, FIXED_POINT_MULTIPLIER, frequencyCoding, height, offsets, pointerCoding, positionCoding, quantum, readerConstructor

Fields inherited from class it.unimi.di.mg4j.index.Index

field, hasCounts, hasPayloads, hasPositions, keyIndex, maxCount, numberOfDocuments, numberOfOccurrences, numberOfPostings, numberOfTerms, payload, prefixMap, properties, singletonSet, sizes, termMap, termProcessor

Constructor Summary

MemoryMappedIndex(ByteBufferInputStream index, int numberOfDocuments, int numberOfTerms, long numberOfPostings, long numberOfOccurrences, int maxCount, Payload payload, CompressionFlags.Coding frequencyCoding, CompressionFlags.Coding pointerCoding, CompressionFlags.Coding countCoding, CompressionFlags.Coding positionCoding, int quantum, int height, TermProcessor termProcessor, String field, Properties properties, StringMap<? extends CharSequence> termMap, PrefixMap<? extends CharSequence> prefixMap, IntList sizes, LongList offsets)

Method Summary

InputBitStream	getInputBitStream(int bufferSizeUnused) Returns an input bit stream over the index.
ByteBufferInputStream	getInputStream() Returns an input stream over the index.

Methods inherited from class it.unimi.di.mg4j.index.BitStreamIndex

featureName, gaussianGolombModulus, getConstructor, getReader, golombModulus, quantumSigma, toString

Methods inherited from class it.unimi.di.mg4j.index.Index

documents, documents, documents, getEmptyIndexIterator, getEmptyIndexIterator, getEmptyIndexIterator, getEmptyIndexIterator, getInstance, getInstance, getInstance, getInstance, getInstance, getReader, getTermProcessor, keyIndex

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

index

protected final ByteBufferInputStream index

The byte buffer containing the index.

Constructor Detail

MemoryMappedIndex

public MemoryMappedIndex(ByteBufferInputStream index,
                         int numberOfDocuments,
                         int numberOfTerms,
                         long numberOfPostings,
                         long numberOfOccurrences,
                         int maxCount,
                         Payload payload,
                         CompressionFlags.Coding frequencyCoding,
                         CompressionFlags.Coding pointerCoding,
                         CompressionFlags.Coding countCoding,
                         CompressionFlags.Coding positionCoding,
                         int quantum,
                         int height,
                         TermProcessor termProcessor,
                         String field,
                         Properties properties,
                         StringMap<? extends CharSequence> termMap,
                         PrefixMap<? extends CharSequence> prefixMap,
                         IntList sizes,
                         LongList offsets)

Method Detail

getInputBitStream

public InputBitStream getInputBitStream(int bufferSizeUnused)

Description copied from class: BitStreamIndex

Returns an input bit stream over the index.

Specified by:

getInputBitStream in class BitStreamIndex

Parameters:

bufferSizeUnused - a suggested buffer size.

Returns:

an input bit stream over the index.

getInputStream

public ByteBufferInputStream getInputStream()

Description copied from class: BitStreamIndex

Returns an input stream over the index.

Specified by:

getInputStream in class BitStreamIndex

Returns:

an input stream over the index.